diff --git a/cura/Machines/MaterialNode.py b/cura/Machines/MaterialNode.py
index 6820c7d740..18db7d982d 100644
--- a/cura/Machines/MaterialNode.py
+++ b/cura/Machines/MaterialNode.py
@@ -89,7 +89,7 @@ class MaterialNode(ContainerNode):
                 else:
                     qualities_any_material = container_registry.findInstanceContainersMetadata(type = "quality", definition = self.variant.machine.quality_definition)
 
-                all_material_base_files = [material_metadata["base_file"] for material_metadata in container_registry.findInstanceContainersMetadata(type = "material", material = my_material_type)]
+                all_material_base_files = {material_metadata["base_file"] for material_metadata in container_registry.findInstanceContainersMetadata(type = "material", material = my_material_type)}
 
                 qualities.extend((quality for quality in qualities_any_material if quality.get("material") in all_material_base_files))